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REVIEW Australian Dental Journal 2009; 54: 9–11 doi: 10.1111/j.1834-7819.2008.01081.x Self-ligating brackets in orthodontics: do they deliver what they claim? PG Miles* *Private Orthodontic Practice, Caloundra, Queensland. ABSTRACT Self-ligating brackets have enjoyed recent popularity in the orthodontic marketplace with various claims made including faster ligation, lower friction, faster treatment, less pain, waking up the tongue, and fewer appointments. Although various designs of self-ligating brackets have been available for many years they have only recently surged in popularity on the back of these claims but what evidence is there to support these claims? This review article examines the current available evidence regarding treatment duration, influence on archform, and the speed of tying and untying self-ligating brackets compared with conventional brackets and methods of ligation. Key words: Self-ligating, orthodontics. (Accepted for publication 29 May 2008.) INTRODUCTION Self-ligating (SL) brackets are becoming more common in the orthodontic marketplace with many manufacturers offering one form or another. Some SL brackets are promoted on the premise that elimination of ligatures reduces friction and allows for better sliding mechanics. If true, SL brackets could reduce the treatment time.1 Self-ligating brackets are not new with the ‘Russell Lock’ edgewise attachment being described in 1935.2 More recently, other designs have appeared including the Speed bracket in 1980, the Time bracket in 1994, the Damon SL bracket in 1996, the TwinLock bracket in 1998, and the Damon 2 and In-Ovation brackets in 2000.3 The popularity and marketing of some of the self-ligating brackets has led other companies to introduce similar systems in an effort to be up with the current trends. In 2008, all major orthodontic companies now offer some form of self-ligating appliance. Claims by manufacturers in their advertising literature range from faster ligation, lower friction, faster treatment, less pain, and fewer appointments but what evidence exists to support these claims? Is orthodontic treatment faster with self-ligating brackets? Several papers have reported that in the laboratory setting self-ligating brackets demonstrate lower friction ª 2009 Australian Dental Association than conventional brackets tied with modules.4–6 Damon described the clinical use of his Damon brackets and proposed that this low friction is a major factor in enabling more efficient treatment.7 However, the assumption has been made that along with low friction in vitro, comes more rapid alignment and a reduction in treatment time in the clinical setting. One of the first clinical studies on treatment efficiency found a mean reduction of four months in treatment time and four visits during active treatment.3 Another clinical study in three practices found an average reduction in treatment time of six months and seven visits for Damon SL cases compared to conventional ligation.1 These reports support a view of clinically significant improvements in treatment efficiency with SL brackets. However, these studies are not clear as to what techniques were used or which variables were controlled. Retrospective studies such as these are potentially biased as there are many uncontrolled factors which may affect the outcome. These include greater experience, differing archwires, altered wire sequences, changes in treatment mechanics, and modified appointment intervals. Observer bias may inadvertently affect the outcome as the practitioner may unknowingly be doing ‘‘a bit more’’ due to enthusiasm with the new product. These other variables may have played a major role in reducing treatment duration. For these reasons, a prospective study with randomized or consecutive assignment is preferred. 9 PG Miles The first published prospective clinical trial compared a Smart-Clip self-ligating bracket with a conventional bracket in the mandibular arch and examined the initial reduction in crowding over the first 20 weeks of treatment.8 This study used identical wire sequences and found no difference between the two bracket types. In a similar study comparing the Damon 2 bracket and conventional brackets, again no difference was found in the clinical ability to align the teeth.9 Another prospective trial comparing Damon and conventional brackets found no significant difference in severely crowded cases but a small difference in favour of the Damon bracket in the moderately crowded cases.10 However, this study used different wire sequences for each bracket type and the thicker rectangular wires used in the Damon cases could explain the more rapid alignment achieved than the round wires used in the conventional brackets. Other prospective evidence is starting to emerge such as a recent abstract presented at the International Association for Dental Research in 2007 which found no difference in total treatment time between conventional edgewise (27.3 ± 6.6 months) and self-ligating (28.0 ± 4.7 months) brackets.11 Another recent paper also found no difference in initial alignment between the Damon 3 bracket and a conventional bracket.12 The only published study so far to evaluate the rate of space closure in extraction cases also found no difference in the rate of tooth movement between a self-ligating bracket and conventional brackets tied with steel ligatures.13 Do self-ligating brackets result in wider arches? Claims have been made that self-ligating brackets can ‘‘waken the tongue’’ resulting in broader archforms than conventional brackets. Research examining the effect of self-ligating brackets on archform has found that conventional and self ligating brackets resolve crowding in a similar manner.10 The lower incisors proclined and slight expansion (1.6 mm) of the dental arches in the molar region occurred. However, the wires used were not of the same shape for the two bracket systems with the Damon 0.014 · 0.025’’ Copper NiTi wire having a wider archform and being thicker compared to the 0.020’’ Sentalloy archwire used with the conventional bracket. This difference in posterior expansion may therefore be solely attributed to the differences in the archwire forms and crosssectional thicknesses and not necessarily related to the bracket used. Another study using low friction ligatures which simulate SL brackets, also found a 1.7 mm increase in intermolar width when compared with conventional module ligation.14 This study also examined any loss of 10 torque control and demonstrated that the molars tipped buccally 4. This supports the possibility that molar expansion observed with SL brackets is related to rolling or tipping of the molars rather than bodily movement. This expansion in the order of 1–2 mm is negligible and could be a spontaneous effect of treatment. Such small changes in molar expansion only result in an additional 0.3 to 0.6 mm in arch perimeter which is clinically insignificant.15 Are self-ligating brackets faster to tie and untie? Self-ligating brackets were initially introduced to reduce the time of ligation, particularly at a time when elastic modules did not exist and only steel ligatures were available. In one study comparing four types of SL brackets with steel ligatures and elastic modules, SL brackets saved 10–12 minutes per patient compared with tying steel ligatures and 2–3 minutes compared with modules, the Speed bracket being the fastest.16 Another study of treatment efficiency found an average time saving from a reduction in archwire placement ⁄ removal of 24 seconds per arch.3 Other studies have supported the improved speed of archwire changes when using SL brackets.4,17 These modest time savings, however, represent only a small fraction of the actual chair time during an orthodontic treatment visit. It would therefore be up to the individual practitioner to determine if this is a significant contribution to the efficiency of their practice. CONCLUSIONS The current prospective evidence regarding duration of treatment indicates that no clinically significant difference exists between conventional brackets and selfligating brackets. Self-ligating brackets have similar effects on archform to conventional brackets. Selfligating brackets offer modest time savings when tying and untying compared with conventional brackets but the time saving varies with the particular design of the SL bracket used. Currently, the evidence is limited and more prospective clinical trials using identical wire sequences and mechanics are required. REFERENCES 1. Eberting JJ, Straja SR, Tuncay OC. Treatment time, outcome, and patient satisfaction comparisons of Damon and conventional brackets. Clin Orthod Res 2001;4:228–234. 2. Stolzenberg J. The Russell attachment and its improved advantages. Int J Orthod Dent Children 1935;21:837–840. 3. Harradine NWT. Self-ligating brackets and treatment efficiency. Clin Orthod Res 2001;4:220–227. 4. Shivapuja PK, Berger J. A comparative study of conventional ligation and self-ligation bracket systems. Am J Orthod Dentofac Orthop 1994;106:472–480. ª 2009 Australian Dental Association Self-ligating brackets 5. Sims APT, Waters NE, Birnie DJ, Pethybridge RJ. A comparison of the forces required to produce tooth movement in vitro using two self-ligating brackets and a pre-adjusted bracket employing two types of ligation. Eur J Orthod 1993;15:377–385. 6. Pizzoni L, Raunholt G, Melsen B. Frictional forces related to selfligating brackets. Eur J Orthod 1998;20:283–291. 7. Damon DH. The rationale, evolution and clinical application of the self-ligating bracket. Clin Orthod Res 1998;1:52–61. 8. Miles PG. Smartclip versus conventional twin brackets for initial alignment: is there a difference. Aust Orthod J 2005;21:123–127. 9. Miles PG, Weyant RJ, Rustveld L. A clinical trial of Damon 2 versus conventional twin brackets during initial alignment. Angle Orthod 2006;6:480–485. 10. Pandis N, Polychronopoulou A, Eliades T. Self-ligating vs. conventional brackets in the treatment of mandibular crowding: a prospective clinical trial of treatment duration and dental effects. Am J Orthod Dentofacial Orthop 2007;132:208–215. 11. Yorita R, Sameshima GT. Comparison of self-ligating and conventional orthodontic bracket systems. J Dent Res (Spec Iss A) 2007:86. Abstract 1918. 12. Scott P, DiBiase AT, Sherriff M, Cobourne MT. Alignment efficiency of Damon 3 self-ligating and conventional orthodontic bracket systems: a randomized clinical trial. Am J Orthod Dentofacial Orthop 2008;134:470.e1–470.e8. ª 2009 Australian Dental Association 13. Miles PG. Self-ligating versus conventional twin brackets during en-masse space closure with sliding mechanics. Am J Orthod Dentofacial Orthoped 2007;132:223–225. 14. Franchi L, Baccetti T, Camporesi M, Lupoli M. Maxillary arch changes during leveling and aligning with fixed appliances and low-friction ligatures. Am J Orthod Dentofacial Orthop 2006;130:88–91. 15. Germane N, Lindauer SJ, Rubenstein LK, Revere JH, Isaacson RJ. Increase in arch perimeter due to orthodontic expansion. Am J Orthod Dentofacial Orthop 1991;100:421–427. 16. Berger J, Byloff FK. The clinical efficiency of self-ligated brackets. J Clin Orthod 2001;35:304–308. 17. Turnbull NR, Birnie DJ. Treatment efficiency of conventional vs self-ligating brackets: effects of archwire size and material. Am J Orthod Dentofacial Orthop 2007;131:395–399. Address for correspondence: Dr Peter Miles Private Orthodontic Practice 10 Mayes Avenue Caloundra QLD 4551 Email: [email protected] 11